1. Field of the Invention
The present invention relates to a device and method for receiving information. More particularly, the invention relates to an information receiving device and method in which an attenuation characteristic of a filter is adjusted to an interfering wave, and an information receiving device and method in which a degree of multipath interference in transmitting information via a ground wave is displayed.
2. Description of the Related Art
In TV broadcasting, digital multi-channel broadcasting via satellite (hereinafter referred to as satellite digital broadcasting) has already been in actual use. In the feature, digitization of ground-wave broadcasting (hereinafter referred to as ground digital broadcasting) can be achieved to be expanded.
However, all conventional ground-wave broadcasting cannot be converted into ground digital broadcasting at one time. There is a certain phase in which ground analog broadcasting and ground digital broadcasting coexist; and in that phase, as shown in FIG. 9, there is a mixed presence of an analog wave used for ground analog broadcasting of the NTSC method (hereinafter referred to as an analog wave) and a digital wave used for ground digital broadcasting (DTV)(hereinafter referred to as a digital wave) on the ground, which is a transmission path. As a result, the analog wave becomes an interfering signal in receiving the digital wave, since the frequency band of the analog wave is adjacent to that of the digital wave and also the analog wave has a larger output power than the digital wave. Particularly, among the analog waves, the lower adjacent sound signal is the biggest obstacle.
Thus, in order to extract a specified channel element of the digital ground wave broadcasting, a filter for eliminating such interfering analog waves is necessary.
It is difficult, however, for a conventional band pass filter to eliminate the lower adjacent sound signal as the biggest problem, since it has a comb-shaped attenuation characteristic, as shown in FIG. 10, and exists adjacent to the channel element to be extracted.
Furthermore, the main obstacles to the transmission of a digital wave on the transmission path for satellite digital broadcasting are weather phenomena such as clouds, rain, or snow, so that the influence from the weather is predictable. To this end, a device for receiving signals is well-equipped for taking countermeasures against these obstacles. In addition, in terms of setting an antenna, the level and C/N (Carrier/Noise) ratio of a signal are checked for arranging in such a manner that the C/N ratio is a maximum value; and the receiving device has a function for measuring the level and C/N ratio of the signal.
Meanwhile, possible obstacles existing on the transmission path for the ground digital broadcasting are geographic features, buildings, and the like, which cause a big problem to the transmission of a digital wave. In particular, multipath interference is an obstacle which is not present in the satellite digital broadcasting system that transmits information via satellite.
Multipath interference also exists in conventional ground analog broadcasting. A ghost image, which is created by multipath interference, gradually changes corresponding to the orientation of an antenna. Thus, a countermeasure against ghost images is to move the antenna while looking at a picture on the TV set so as to be arranged in an orientation that is least affected by multipath interference.
The influence of multipath interference in ground digital broadcasting, however, is eliminated or corrected by an error-correcting function, which is an advantage in the use of digital signals, even if the antenna is arranged to be deviated slightly from the best orientation. Therefore, it is impossible to use the method for determining a direction in which the least amount of ghost image occurs by looking at the picture on the TV set as in the case of ground analog broadcasting above, so that the determination of the best orientation for the antenna cannot be performed.
Accordingly, the present invention has been made to solve these problems. It is a first object of the present invention to provide a method for eliminating an interfering wave by coinciding the peak of an attenuation characteristic of a filter with the peak of the interfering wave.
Furthermore, it is a second object of the present invention to provide a method for determining the best orientation for an antenna by visually displaying multipath interference.
According to a first aspect of the present invention, there is provided an information receiving device including a receiving unit for receiving an information signal and an extracting unit for extracting a signal of a specified band from the information signal received by the receiving unit; in which the peak of an attenuation characteristic of the extracting unit coincides with the peak of an interfering signal adjacent to a signal to be extracted.
According to a second aspect of the present invention, there is provided an information receiving method including a receiving step for receiving an information signal and an extracting step for extracting a signal of a specified band from the information signal received by the receiving step; in which the peak of an attenuation characteristic of the extracting step coincides with the peak of an interfering signal adjacent to a signal to be extracted.
According to a third aspect of the present invention, there is a providing medium for providing a computer program, which includes a receiving unit for receiving an information signal, an operating unit for calculating the strength of a multipath element, and a display-controlling unit for controlling a display of the strength of the multipath element calculated by the operating unit.
According to a fourth aspect of the present invention, there is provided an information receiving method which includes a receiving step for receiving an information signal, an operating step for calculating the strength of a multipath element, and a display-controlling step for controlling a display of the strength of the multipath element calculated by the operating step.
Regarding the information receiving device described in the first aspect of the invention, the receiving unit receives an information signal, while the extracting unit extracts a signal of a specified band from the information signal received by the receiving unit.
In the information receiving method described in the second aspect of the invention, the receiving step receives an information signal, while the extracting step extracts a signal in a specified band from the information signal received by the receiving step.